1. Field of the Invention
This invention relates generally to flexible optical surfaces usable as filters, refractors, reflectors and the like, and more particularly to an improved controllable surface for optical applications with a flat state that is not influenced by repeatedly rolling and unrolling into a coiled state, and to a method for making the controllable surface.
2. Description of the Prior Art
An optical surface, film and laminate has optical applications in articles of manufacture ranging from a projector screen to a solar film. Various other optical applications include use in a television screen, highway reflector, sign or the like. For a desired application, the optical surface can be formed from a single substrate or from a wide variety of layered constructions. Some optical surfaces can be adapted with a precise optical characteristic or function to modulate incident light energy in accordance with the various laws of optics such as, for example, diffraction, diffusion, dispersion, refraction or reflection. The present invention provides both a controllable surface when unrolled, and permits the use of precision optical characteristics or functions. Furthermore, by forming the controllable surface using flexible, coilable spring-like materials having superior lay-flat characteristics, the present invention can be applied to many articles of manufacture that today use a rigid or non-rigid support substrate.
Some current designs of controllable surfaces use a rigid support substrate. The rigid support substrate is relatively stiff and thus can easily provide a predictable and usable planar surface area to define the controllable surface needed for optical applications. A spherically-curved rigid support substrate can be used to make the controllable surface more orthogonal to the incident light energy generated from a point source as is illustrated in U.S. Pat. No. 3,408,132 to Chandler et al., and thus can increase and control the light reflected to an audience viewing zone. The controllable surface formed using rigid support substrates can eliminate the problem of hot spotting as occurs with flat surfaces when the dynamic brightness range exceeds the tolerance of photopic vision. For example, in certain applications an optical pattern can be imprinted in or secured to the controllable surface to modulate incident light energy. The optical pattern can have the precision optical characteristic such as a differential refraction pattern to increase the dynamic range or gain of the optical surface. Patterns using multiple precision optical characteristics can also modulate incident light energy to a greater or lesser degree according to particular areas or zones of the optical surface. However, disadvantages of the rigid support substrate include storage problems where the rigid support substrate cannot be rolled-up and effectively transported. Other disadvantages include the optical surface being permanently secured to the rigid support substrate, being relatively bulky and unmovable, and requiring costly manufacture or installation.
Alternatively, known optical surfaces formed using a flexible or non-rigid support substrate cannot provide the controllable surface for optical applications requiring a pattern of precision optical characteristics because a non-uniform surface such as undulations, edge-curl or other surface deformations can negate the beneficial effects of the pattern. Most known non-rigid support substrates are manufactured from conventional polymeric materials such as nylons, vinyl, acetals, polyolefins, or other fiber reinforced materials with a modulus of elasticity of about 15,000 p.s.i. The resulting flexible optical surface can be rolled-up but does not have a controllable surface when unrolled. This feature of known non-rigid support substrates precludes the use of precise optical functions, particularly if the above-identified materials contain a plasticizer. For this reason, most applications for these optical surfaces using conventional non-rigid support substrates have not included precision optical characteristics or have reduced performance with restricted gains of 2 gains or less.
Projection screens are increasingly more diverse and sophisticated using precision optical characteristics, various combinations of optical patterns and a wide variety of layered constructions. An example of a projection screen is illustrated in U.S. Pat. No. 4,191,451, by the same inventor as the present application, and is hereby incorporated by reference. The patent relates to optical surfaces, and in particular to the forming of the optical layer for a multi-layered optical surface and method for manufacturing the same. The optical layer is formed with a pattern of light affecting elements to control the optical characteristics of the projection screen. The optical layer is secured to either a rigid or flexible support substrate made from conventional materials. However, the present invention overcomes the many disadvantages of known rigid and non-rigid support substrates made from conventional materials to provide a high gain, controllable surface using a non-rigid support substrate and precision optical characteristics.
Optical surfaces have applications in solar films. Solar films are mostly used to change the amplitude, magnitude or direction of incident light energy depending upon the application desired such as to reflect light energy in the summer or absorb light energy in the winter, or both. Known solar films are thin and flimsy requiring these to be permanently secured to a rigid support substrate such as glass in buildings, automobiles, etc. It would be advantageous if an all weather, relocatable roll-up solar film could be formed to function as a window shade and further to have precision optical characteristics incorporated thereon.
Accordingly, there is a need for a flexible optical surface, film or laminate with the advantages of the controllable surface with precision optical characteristics for such applications as roll-up projection screens. There is also a need for a simple, efficient and inexpensive method of producing these flexible optical surfaces to varied specifications. Such a method should be capable of producing high quality, superior controllable surfaces with optics at a reduced cost of manufacture.